1. Field of Invention
The invention relates to a cutting blade for a reaper that serves to cut fruit, branches, roots or the like of plants by reciprocation of the cutting blade.
2. Description of the Related Art
Cutting blades for a reaper that serve to cut fruit, branches and leaves or roots of plants by utilizing reciprocation of the cutting blade exist in the prior art, for example, Japanese Laid-open Patent Publication No. Hei 7-95827 which discloses a cutting blade for cutting the roots of plants. FIGS. 5A, 5B are views showing the prior art structure of the cutting blade for the root cutter, FIG. 5A being a front view and FIG. 5B being a sectional view taken along the line Vbxe2x80x94Vb of FIG. 5A.
In FIGS. 5a, 5B, the exemplary prior art cutting blade 101 for a root cutter is constructed such that a plate-shaped blade member 103 extends like a rectangular plate having a predetermined width from the tip part of a bar-shaped shank member 102. When the cutting blade 101 for the root cutter having such a structure is used, a base end portion of the shank member 102 thereof is fixed to the root cutter (not shown) including a striking mechanism such that it can axially reciprocate by a predetermined distance. Then, the cutting blade 101 axially reciprocates upon receipt of striking force from the root cutter, thereby cutting the roots of plants and the like.
There has been known a method for manufacturing the cutting blade 101 by integrally forming the shank member 102 and the plate-shaped blade member 103 or by welding the plate-shaped blade member 103a to the shank member 102a, as shown in FIGS. 6 and 7. For example, a rectangular notch portion 104a is formed on the base end portion of the plate-shaped blade member 103a as shown in FIGS. 6A and 6B. A tip portion of the bar-shaped shank member 102a is fitted into the notch portion 104 of the plate-shaped blade member 103a, and the fitted tip portion of the shank member 102a is welded to an edge portion of the notch portion 104a (a portion of the plate-shaped blade member 103a that fronts the notch portion 104a). Thus, the assembled cutting blade 101a is manufactured. Alternatively, as shown in FIGS. 7A, 7B, 7C and 7D, a slit 106b extending in the axial direction is formed in the central portion of a tip portion of the shank member 102b. The base end portion of the plate-shaped blade member 103b is fitted into the slit 106b of the shank member 102b, and the fitted base end portion of the plate-shaped blade member 103b is welded to the tip portion of the shank member 102b. Thus, the cutting blade 101b is manufactured.
It is hard to manufacture the cutting blade 101 for the root cutter by integrally forming the plate-shaped blade member 103 and the shank member 102 by forging, and, in particular, to manufacture, by the forging, the cutting blade 101 including a plate-shaped blade member which is thin and has a large area because of man-hour time that is taken.
In the method for manufacturing a cutting blade as shown in FIGS. 6A, 6B, it is difficult to position the plate-shaped blade member 103a with respect to a shaft axis of the shank member 102a in a direction of the thickness without an offset when the shank member 102a is welded to the plate-shaped blade member 103a. 
If the plate-shaped blade member 103a is welded to have the offset with respect to the shaft axis of the shank member 102a, the cutting performance of the cutting blade 101a is affected. Therefore, it is necessary to specially use a jig for fixing the plate-shaped blade member 103a to the shank member 102a. Moreover, welding the plate-shaped blade member 103a to the shank member 102a is sequentially performed along the shank member 102a from an end thereof. Therefore, the welding is greatly affected by a distortion (thermal distortion) or the like. Consequently, the skills for the welding is required in order to reduce the influence of the welding distortion or the like as much as possible.
In the method for manufacturing a cutting blade shown in FIGS. 7A, 7B, 7C, 7D, it is difficult to position the plate-shaped blade member 103b in a transverse direction with respect to the shank member 102b during the welding. For this reason, the same problems as in FIGS. 6A, 6B arise with regard to the offset of the plate-shaped blade member 103b in the transverse direction. Furthermore, an innermost wall surface 106b of the slit 106b of the shank member 102b is not welded. Therefore, there is a problem in that the strength of the connecting portion of the shank member 102b and the plate-shaped member 103b is reduced.
In order to solve the above-mentioned problems, it is an object of the invention to provide a cutting blade for a reaper, which can easily position members to be welded, can reduce a welding distortion, can fully ensure the strength of a shank member and can be manufactured easily.
The invention provides a cutting blade to be used for a reaper that serves to cut off plants by reciprocation of the cutting blade, comprising, a bar-shaped shank member which has a groove formed on an outer peripheral face of a tip portion to extend in an axial direction and whose base end portion is to be fixed to the reaper, and a plate-shaped blade member having a notch portion formed on a base end portion and having a cutting portion formed in a tip portion, the cutting portion extending in a direction which is substantially perpendicular to the axial direction of the shank member, wherein the tip portion of the shank member is fitted into the notch portion of the plate-shaped blade member in such a manner that an edge portion of the notch portion is fitted into the groove, and the fitted tip portion of the shank member is welded to a portion of the plate-shaped blade member which is located around the tip portion. With such a structure, the plate-shaped blade member is positioned in a direction of the thickness and width (transverse) with respect to the shank member without an offset from a shaft axis of the shank member through the fitting of the groove of the shank member to the edge portion of the notch portion of the plate-shaped blade member. Moreover, a thermal distortion can be relieved by the grooves of the shank member, and the strength of the shank member can also be ensured easily because an unwelded face in a cross-sectional direction is not formed in the shank member. Accordingly, it is possible to easily manufacture a thin plate-shaped cutting blade having a large area.
In the above-mentioned case, preferably, two grooves of the shank member are formed on the outer peripheral face of the shank member along the shaft axis thereof to front toward opposite directions with each other on the same plane, and the edge portions of the notch portion of the plate-shaped blade member which are opposite to each other are fitted into the grooves respectively.
These objects as well as other objects, features and advantages of the invention will become more apparent to those skilled in the art from the following description with reference to the accompanying drawings.